Continuous power/signal conductor and cover for downhole use

ABSTRACT

Conductors are placed in insulator which acts as a spacer/centralizer for the conductors, which are in turn mounted within tubing. The void spaces between the insulator and the tubing inside wall can be filled with a sealing material. Alternatively, the voids around the substantially centralized conductors can be used as flow channels for the transmission of fluid pressure to a remote location, such as downhole. The conductors are protected because they are kept away from the tubing wall and can be further protected by the addition of the sealing material.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/790,036,filed Jan. 28, 1997 now abandoned, which is a continuation-in-part ofapplication Ser. No. 08/361,592, filed on Dec. 22, 1994, now abandoned,

FIELD OF THE INVENTION

The field of this invention relates to control lines which can transmitfluids to remote locations and, more particularly, control lines whichcan be used in oil and gas operations, such as subsea, wherein it isalso advantageous to transmit electrical, optical, or any other signalsto a remote point.

BACKGROUND OF THE INVENTION

In many applications in the oil and gas industry it is desirable totransmit fluid pressure to a remote location for actuation of equipment,as well as to run electrical or other types of conductors for eithertransmission of signals or power to or from the surface to a subsurfacelocation or for other reasons. Typically, a conduit which, if small andsufficiently flexible, can be unrolled from a roll is run along side theproduction tubing or otherwise into a borehole. If signals are to besent from the wellbore to the surface electrically, a separate cable hasbeen used, which many times is bundled to the exterior of the controltubing such that the hydraulic signals pass through the control tubingwhile the electrical, generally low-voltage signals, which record anynumber of downhole well conditions or operate low-voltage equipment, usethe adjacent cable for transmission of such signals. It has also beenattempted in the past to run the electrical signal cable into andthrough a coiled tubing unit. In those instances, the signal cable isexternally shielded to prevent any signal interference from thesurrounding tubing structure. One of the problems in this type ofinstallation has been that the shielded cable would develop flaws orpinholes in its outer protective casing, which would then allow thefluids to migrate into the cable, damaging the signal conductorstherein. Additionally, another problem encountered with such designs isthat the conductor cable running through the tubing could in many placesorient itself adjacent the tubing wall, particularly if the well was inany way deviated. The contact between the electrical cable and thetubing wall could cause two problems. First, it could cause abrasion ofthe shield material against the inside surface of the tubing wall, whichultimately would result in compromising the integrity of the coveringfor the conductors. This, as previously described, could cause abreakdown in the ability to transmit signals through the conductors.Additionally, close proximity to the tubing wall also rendered theinternal cable vulnerable to damage from mechanical impacts on thetubing in situations where the cable is located up against the insidetubing wall. Such impacts could cause dents in the tubing wall, whichwould translate directly to the cable damaging and perhaps severing thecable. Finally, and to a lesser extent, close proximity to the insidewall of the tubing also created some potential risk of signalinterference from the metallic tubing wall.

Space is routinely at a premium in oil and gas installations,particularly in offshore applications. It is frequently desirable thatthe external control tubing have a small diameter as possible, while, atthe same time, it must have the necessary rigidity and internal diameterto allow accommodation of an internal conductor. What is desirable andheretofore lacking in the known equipment is a compact design where aconductor can be effectively isolated and located reasonably centrallyto the tubing to minimize damage to the cable from impacts to thetubing. Additionally, with the conductors positioned within the tubingand their position retained away from the tubing wall, the spaces aroundthe conductor can be used to allow fluid flow or, in the alternative,can be filled with a sealing material which provides further durabilityto the assembly of conductors, insulators/centralizers, and voidsealant, all disposed within the tubing.

SUMMARY OF THE INVENTION

Conductors are placed in insulator which acts as a spacer/centralizerfor the conductors, which are in turn mounted within tubing. The voidspaces between the insulator and the tubing inside wall can be filledwith a sealing material. Alternatively, the voids around thesubstantially centralized conductors can be used as flow channels forthe transmission of fluid pressure to a remote location, such asdownhole. The conductors are protected because they are kept away fromthe tubing wall and can be further protected by the addition of thesealing material.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the tubing, showing the conductor thereinwith a filling in between.

FIG. 2 is the view of FIG. 1 without the filling.

FIG. 3 is the view of FIG. 2, with a schematic representation of acombination of a hydraulic and electrical element showing a typicalapplication of the apparatus of the present invention.

FIG. 4 is a section showing the wrap of insulation between the conductorand the shaped insulator.

FIG. 5 is another section illustrating the notch feature on the fins ofthe shaped insulator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates the apparatus A of the present invention. Itcomprises an external housing or tube 10 which can be made in a varietyof corrosion-resistant materials, including metals such as 316 StainlessSteel, Inconel, as well as rigid plastic materials. Inside the housing10 is a spacer 12. Inside the spacer 12 is conductor or conductors 14.Conductors 14 can be one or more strands which collectively can transmita signal. A strand or groups of strands can be separately bundled andshielded before being mounted to the spacer 12. In this manner, thetubing or housing 10 carries a plurality of potential signal or powertransmission avenues within the same spacer 12. In the preferredembodiment, the spacer 12 has a plurality of radial projections 16,which are spaced at 120° intervals, and which extend radially from a hubor core 17, to create three parallel flowpaths 18, 20, and 22. Theflowpaths can be used as such or can in the alternative, as shown inFIG. 1, be filled with an epoxy 24. By adding the epoxy 24, additionalprotection for the conductors 14 is provided. The radially extendingmembers 16 also help to centralize the conductors 14 and keep them awayfrom the outer housing 10. By centralizing the conductors 14, they areless prone to be damaged. Furthermore, the control signals passingtherethrough are less likely to suffer interference from adjacent metalcomponents, such as housing 10. When the assembly is put together, asshown in FIG. 1, with the flowpaths 18, 20, and 22 further filled withepoxy, the assembly becomes more durable in withstanding mechanicalshocks but yet remains sufficiently flexible to allow coiling of thehousing 10 onto a roll (not shown) for easy storage and dispensing whenneeded. While the preferred embodiment indicates the conductors to becentralized, an offset location, but removed from the housing or tubing10, is still within the purview of the invention. While three radialextensions 16 are shown in the preferred embodiment, differentconfigurations can be employed to accomplish the positioning feature ofgetting the conductors 14 away from the tubing 10. For example, a feweror greater number of radially extending fins, such as 16, can be used.Different geometric shapes that extend from a hub that encircles theconductors 14 can be used, such as a single helix or a multiple helix,as long as their spacing is not so great or radial extension too smallso as to allow the hub that surrounds the conductors to engage the innerwall of the housing or tubing 10. The conductors 14 can be furtherwrapped with a signal-insulating material prior to being inserted intothe spacer 12. The insulating material is illustratively shown in FIG. 4as item 32. As shown in FIG. 4, it wraps around the conductor 14 suchthat the hub 17 is applied over the signal-insulating material 32. Theinsulation 32 can be in a single or multiple layers applied to theconductor 14 before application of the hub 17 and the extending member16. The insulation 32 can be made from a variety of materials, includingbut not limited to varnish composites, bonded or unbonded tapes appliedeither longitudinally or spirally with overlap, sintered powders orextruded compounds. The insulation 32 can also be extruded over theconductors 14. Co-extrusion of the insulation 32 with the hub 17 andextending member 16 can be accomplished if the appropriate materials areselected. Alternatively, multi-pass extrusion techniques can be used.Layer-to-layer bonding may be desirable but not required for thecomposite construction; thus, the insulation 32 can be selectivelybonded to the conductors 14 or the hub 17, depending on the application.Dissimilar materials can be used as between the hub 17 and the insulator32. The insulator 32 can be made from polyimide tape, with the hub 17made of ETFE or PVDF (polyvinyl difluoride). The addition of theinsulator 32 enhances the electrical integrity of the conductors 14,particularly if the outer tubing tube 10 is damaged in any way. Thefiller material 24 also aids the retention of electrical integrity tothe conductor 14. The insulating material 32 can also includehigh-temperature compounds which contain fluoride compounds andsilicones or, in the alternative, mineral insulation. Use of thesematerials, in combination with the epoxy 24 in the flowpaths 18, 20, and22, adds crush resistance to minimize insulation compromise.Additionally, the presence of the insulating layer 32 facilitates themaking of end connections. When the hub 17 and extending member 16 arebent at a termination to deliberately expose the conductor 14 for makingconnections, the presence of the insulating layer 32 promotes crackingof the hub 17 in reaction to bending so that a portion of the hub 17 andthe extending member 16 can be removed easily from the end of theconductor 14. The addition of the insulating layer 32 minimizes the riskof damaging the conductors 14 in the bending process that is used toremove the last segment of the hub 17 from an end of the finishedassembly to facilitate the making of a connection. Without theinsulating layer 32, the degree of bending that may be necessary tobreak the hub 17 to get it off of the conductor 14 may also result indamage to the conductors 14, which would be undesirable. The insulatinglayer 32 remains intact after the hub 17 is scored and snapped off.

In the preferred embodiment, the spacer assembly 12 is extruded onto theinsulator 32 which is mounted over conductors 14 while the tubing, whichoriginally comes in a flat sheet, is rolled into a tubing form and theseam 11 is welded around the spacer 12. The assembly is so oriented sothat the seam which forms the tubing 10 is not aligned with any one ofthe radially extending members 16 to avoid any damage to them during thewelding or brazing process. In this manner, a continuous-length segmentof the apparatus A can be assembled and rolled onto a reel as it is puttogether. The length can vary depending on the distances from thesurface to the downhole components in a typical application. Theconnections are at either end of the continuous length, with oneconnection at the downhole equipment and the other at the surface.

FIG. 3 illustrates the application of the apparatus A in a schematicmanner to allow for operation of a hydraulically actuated component, aswell as at least one electrically actuated component. The hydraulicallyactuated component is schematically illustrated as a valve 26, but couldin an actual application could be any one of a number of differentcomponents. The electrical segment is illustrated as box 28. In aparticular application, the hydraulically actuated component can be adownhole valve which is operated by a shifting sleeve or some otherhydraulically-actuated operator, and the box 28 can be a sensor orsensors which can respond to indicate whether a shaft has turned, or asleeve has shifted, or the like. Separate signal-carrying capacity canbe provided within hub 17 if conductors are separately bundled andinsulated as a group prior to having hub 17 extruded over them. In thisway, multiple signal or error transmission functions can besimultaneously serviced.

Many potential applications are possible for the apparatus A of thepresent invention. For example, the apparatus A can be used to operate asolenoid-operated safety valve with hydraulic communication capabilityfor an insert valve. The apparatus A can also be used for proximityindicators or position sensors to indicate if a valve is full open orfull closed. An electrically operated mechanism to lock a flapper on asubsurface safety valve in the open position can be operated with theapparatus A of the present invention. Other applications include: (1)downhole control line pump and reservoir to eliminate hydrostatic headon deep-set valves, (2) a solenoid to operate the flapper on asubsurface safety valve without stroking the flow tube, (3) anelectrical assist mechanism for stuck flow tubes, (4) electricalcommunication for wireline tools, (5) electrical/hydraulic shuttle valveoperation for ultra deepset applications, (6) electrically operatedequalizing devices, (7) electrically controlled adjustable orifices orchokes, (8) flowing pressure and temperature transducers at subsurfacesafety valves, (9) electrically operated communication features forinsert valves, (10) control line pressure transducers, (11) backupelectrical actuators in case of hydraulic failure, (12) pH sensors at avalve to monitor control line or tubing fluids, (13) load cellcommunication to determine valve position, packing element, or a slipload, (14) constant power source for an electromagnetic valve, (15)proximity sensors for subsea actuators, (16) electrically operatedlock-open devices for a subsea actuator, (17) electrically operatedlock-close devices for a subsea actuator, (18) electrical permanentlock-open device for subsurface safety valves, (19) electrical overridefor subsea actuator to open gate valve, and (20) electrical releasemechanism for subsea actuator to release connection between the actuatorand the valve stem during removal. These are some of the applications,although many others can be employed without departing from the spiritof the invention.

To the extent the passages 18,20, and 22 can be isolated from each otherseparate pressure signals in each path can be transmitted to a remotepoint such as subsea.

In the preferred embodiment, the spacer is made from extruded TEFZELO®,which is a PTFE fluorocarbon material available from E.I. Dupont. In thepreferred embodiment, if encapsulation of the spacer 12 is desired, anepoxy resin, which is a mixture of a plasticizer, a resin, and a curingagent, provides an effective gas/fluid block if the tubing 10 ispenetrated. Other materials can be used in lieu of the epoxy resin ifthey are pumpable and can provide the shock protection and gas/fluidblocking protection for the conductor 14. An alternative embodiment canbe the provision of the outer jacket 10 in a material calledSANTOPREME®, which is available from Monsanto Company, St. Louis,Missouri.

One of the advantages of the construction of the apparatus A is that theouter jacket 10 can be stripped off, as required, without damaging theinner conductor 14. In the preferred embodiment, a bundle of 18 gaugecopper conductor forms the main conductor 14 running through the spacer12. The use of the epoxy material, which acts as an incompressiblefluid, significantly increases the compressive and collapse strength upto four times that of an unfilled tube. Under compression, the epoxymaterial acts as a fluid cushion and provides additional protection thatis now not available with other types of downhole cable. The exteriorhousing or jacket 10 also shields against electrical noise, while theentire assembly is economical and permits multiple reruns. The fillertotally fills the flowpaths 18, 20, and 22, but partial filling is alsowithin the scope of the invention.

In the preferred embodiment, the housing 10 has a seam which iselectron-beam welded. The spoke-like profile of the preferred spacer 12allows the insulation of the conductors 14 to be oriented during thewelding process to put a seam between the two spokes, thereby reducingthe possibility of contaminating the well with insulation material andreducing the heat transfer from the insulation to the newly formed weld.The method of assembly thus improves the quality of the finishedproduct. With the epoxy resin filler, or other equivalent materials, thecompressive strength of up to 30,000 psi is obtained.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction, may be made without departing from the spirit of theinvention.

We claim:
 1. An assembly for power or signal transmission between the surface of a well and a downhole component, comprising:a continuous metallic cover tube made from at least one sheet rolled into a tube to create a long seam and being of a sufficient length to reach, at one end, from a surface of a well to, at another end, a downhole component without any Intermediate connections; at least one conductor extending continuously through said cover tube from said surface to said downhole component; a nonmetallic spacer comprising at least one extending member extending from a core which surrounds said at least one conductor to space said at least one conductor; and said cover tube Is formed by rolling said sheet over said at least one conductor to create said seam offset from said at least one extending member so that a weld of said seam is not damaged by said at least one extending member, as said cover tube is formed over said spacer.
 2. The assembly of claim 1, wherein: said spacer is continuous.
 3. The assembly of claim 2, wherein:said spacer defines a continuous passage through said cover tube.
 4. The assembly of claim 3, wherein:said passage is substantially filled with a substantially incompressible material, said material prevents gas or liquid flow therethrough if said cover tube is compromised.
 5. The assembly of claim 3, wherein:said spacer comprises at least one fin extending from said core which surrounds said at least one conductor.
 6. The assembly of claim 5, wherein:said fin has a core end where it is connected to said core and a cover tube end where it contacts said cover tube, said core end configured to preferentially fail under stress loading to facilitate removal of said fin from adjacent said surface or downhole component ends of said cover tube to facilitate connection of said at least one conductor.
 7. The assembly of claim 1, further comprising,an Insulator covering said at least one conductor and disposed between said at least one conductor and said spacer.
 8. The assembly of claim 7, wherein:said insulator is disposed over said at least one conductor In such a manner that It will break rather than said at least one conductor breaking when said spacer is exposed at either end of said cover tube and bent to facilitate removal of excess of said spacer and said Insulator when making a connection with said at least one conductor.
 9. The assembly of claim 7, wherein:said insulator and said spacer are co-extruded over said at least one conductor.
 10. The assembly of claim 7, wherein:said insulator is wrapped around said at least one conductor and said spacer is extruded over said insulator covering.
 11. The assembly of claim 1, wherein:said cover tube with said at least one conductor and said spacer therein is sufficiently flexible to be coiled on a reel prior to use.
 12. The assembly of claim 1, wherein:said spacer is extruded over said at least one conductor. said insulator and said spacer are co-extruded over said at least one conductor.
 13. The assembly of claim 1, further comprising:an insulator covering said at least one conductor and disposed between said at least one conductor and said spacer.
 14. The assembly of claim 13, wherein:said insulator is disposed over said at least one conductor in such a manner that it will break rather than said at least one conductor breaking when said spacer is exposed at either end of said cover tube and bent to facilitate removal of excess of said spacer and insulator when making a connection with said at least one conductor.
 15. The assembly of claim 14, wherein:said insulator and said spacer are co-extruded over said at least one conductor.
 16. The assembly of claim 13, wherein:said insulator is wrapped around said at least one conductor and said spacer is extruded over said insulator covering. 